This invention relates to a suspension system for a four-wheeled vehicle and more particularly to an improved, simplified and more effective suspension system for controlling all running conditions, which the vehicle encounters.
An arrangement has been proposed for suspending four-wheeled vehicles that employs individual shock absorbers at each wheel which have a relatively simple damping arrangement in them. However, the shock absorbers of paired wheels are coupled together with a pressure control mechanism that provides additional damping under certain characteristics. This type of system is show in Japanese Published Application. Hei 06-72127 and in its United States equivalent, U.S. Pat. No. 5,486,018, entitled xe2x80x9cSUSPENSION SYSTEM FOR FOUR-WHEELED VEHICLESxe2x80x9d issued Jan. 23, 1996 and the assigned to the assignee hereof. That patent shows a number of arrangements of such interrelated suspension systems. One that shows considerable sophistication appears in FIG. 13 of that U.S. patent and is reproduced here a FIG. 1. The details of the interrelationship between the various shock absorbers and the control arrangement is shown in more detail in FIG. 2.
As shown therein, there are four shock absorbers indicated at 11LF, 11RF, 11LR and 11RR comprising the cushioning units associated with the four wheels of the vehicle at its corners. Each of the shock absorbers 11 is mounted between the wheel suspension system and the vehicle body in a manner, which will be generally described, as will the individual construction of each shock absorber 11, which are identical.
Each shock absorber 11 includes a body portion 12 that defines a cylinder bore in which a piston 13 is supported. The piston 13 divides the cylinder bore into an upper chamber 14 and a lower chamber 115. A piston rod 16 extends through the upper chamber 14 and has a trunion 17 for attachment to the wheel suspension system or the vehicle body. A trunion 18 on the cylinder 12 accommodates the other connection.
A passageway 19 extends between the chambers 14 and 15 and has an orifice 21 for providing individual wheel damping control.
The individual shock absorbers 11 are interconnected with each other by means of an interconnecting control arrangement, indicated generally by the reference numeral 22. This control arrangement 22 includes individual passageways 23, 24, 25 and 26, which interconnect the chambers 15 of the shock absorber 11LF, 11RF, 11LR and 11RR with a pressure control, indicated generally by the reference numeral 27.
This pressure control 27 is shown in more detail in FIG. 2 and includes a body 28 in which four cylinder bores 29, 31, 32 and 33 are formed. Pistons 34, 35, 36 and 37 reciprocate in the cylinder bores 29, 31, 32 and 33, respectively. These pistons 34, 35, 36 and 37 are all connected for simultaneous movement by means of a bridging member 38, which extends into a pressurized gas chamber 39. This chamber 39 is pressurized to a suitable pressure with an inert gas such as nitrogen.
Thus, each shock absorber chamber 15 is in communication with a respective one of pressure control volumes 41, 42, 43 and 44 formed in the control body 28 between the pistons 34, 35, 36 and 37 and the cylinder bores 29, 31, 32 and 33, respectively.
Certain of the shock absorber chambers 15 are paired with each other via communicating passageways 45, 46 and 47 which connect the control pressure chambers 41 and 42, 42 and 43, and 43 and 44 together. Flow controlling orifices 48, 49 and 51 are positioned in the passages 45, 46 and 47, respectively.
When each wheel encounters the same obstacle at substantially the same time, each piston 13 will move in its respective shock absorber 11 to decrease the volume in the chamber 15. This motion is dampened by the flow through the orifice 21 into the chamber 14. However, since the piston rod 16 extends into the chamber 14 and displaces some of its volume, more fluid is expelled through the conduits 23, 24, 25 and 26 than the chambers 14 can accommodate. This excess displaced fluid flows to the chambers 41, 42, 43 and 44, respectively. Since equal volume of fluid is displaced from each shock absorber 11, the pistons 34, 35, 36 and 37 will move uniformly and the control device 27 will provide no additional damping.
If, however, there is a pitching motion, which tends to cause the vehicle weight to shift to the front, there will be more compression in the chambers 15 and 16 of the shock absorbers 11LF and 11RF than in the shock absorbers 11LR and 11RR. In fact, these shock absorbers will tend to move in the opposite direction. When this occurs, flow will pass through the orifices 48 and 51 from the chambers 41 and 44 into the chambers 42 and 43, respectively. Hence, this will provide damping from the pitching action, which might otherwise occur in addition to the damping provided by the individual shock absorbers 11.
In a similar manner, if the vehicle is rounding a curve which tends to cause the body to roll to the right i.e. when making a left-had turn, fluid will flow from the shock absorber 11LR to the shock absorber 11RR through the orifice 49 so to resist roll. However, there is no such roll resistance provided at the front and thus, it is very difficult to set the arrangement for overall damping to suit all conditions.
It is, therefore, a principal object to this invention to provide an improved shock absorber and suspension arrangement for a four-wheeled vehicle that will provide good damping for individual wheel suspension travels and also so as to preclude roll and pitch in all directions.
It a further object to this invention to provide an improved and simplified suspension system of this type and that will achieve these results.
A first feature of this invention is adapted to be embodied in a suspension system for a vehicle having at least four wheels, each of which is supported for suspension movement by a vehicle body. Each of four damping elements, each having a pair of relatively moveable members defining a respective first chamber, are interposed between a respective one of the wheels and the vehicle body for varying the volume of the first fluid chamber upon suspension movement of the respective one wheel. Each of the damping elements has a respective damping arrangement for damping the flow of fluid from the respective one of the first fluid chambers. A first conduit interconnects a first pair of the first fluid chambers of two of the damping elements and a first control arrangement is provided for precluding fluid flow through the first conduit in response to a first suspension condition and for providing a damped flow through the first conduit in response to a second suspension condition. A second conduit interconnects the second pair of the first fluid chambers of the remaining two of the damping units. A second control arrangement is provided in the second conduit for precluding fluid flow through the second conduit in response to a first suspension condition and for providing a damp flow through the second conduit in response to a second condition. A third conduit interconnects a third pair of the first fluid chambers other than those paired by the first and second conduits. A third control arrangement is provided in the third conduit for precluding fluid flow through the third conduit in response to a first suspension condition and for providing a damped flow through the third conduit in response to a second suspension condition. A fourth pair of the first fluid chambers other than those paired by the first, second and third conduits are interconnected by a fourth conduit. A fourth control arrangement is provided in the fourth conduit for precluding fluid flow through the fourth conduit in response to a first suspension condition and for providing a damped flow through the fourth conduit in response to a second suspension condition.
Another feature of the invention is embodied in an accumulator and control device for interconnection between four hydraulic damping units for controlling their respective damping action. The device comprises a housing defining first, second, third and fourth fluid chambers each adapted to exchange fluid with a respective one of said damping units. First, second, third and fourth accumulator pistons are each received in a respective one of the fluid chambers. The pistons and fluid chambers each define a fluid side for exchanging hydraulic fluid with the respective hydraulic damping unit and an accumulator side for maintaining a pressure in the hydraulic fluid. Four conduits each having a flow control therein interconnect different pairs of the fluid chambers and control the flow therebetween.